A relatively new type of image-sensing device employs an odd-symmetry grating to project an interference pattern for capture by a photodetector array. The grating offers considerable insensitivity to the wavelength of incident light in a wavelength band of interest, and also to the manufactured distance between the grating and the array. The grating produces an interference pattern quite different from the captured scene, but that contains sufficient information to mathematically reconstruct the scene or aspects of the scene. Images can thus be captured without a lens, and cameras can be made smaller than those that are reliant on lenses and ray-optical focusing. Embodiments of such image-sensing devices are detailed in U.S. Publication 2014/0253781, which issued on 18 Aug. 2015 as U.S. Pat. No. 9,110,240 and is incorporated herein by reference.
Some imaging applications do not require reconstruction of the imaged scene. For example, tracking movement of a point source using an odd-symmetry grating does not require the overall scene be reconstructed. Where image reconstruction is desired, however, the mathematical operations used to invert the raw image data can be computationally cumbersome.